TetraPond Green Free UVC Adapter Kit is used to help ensure your UVC fits your pump. This UVC Barbed swivel adapter does not fit the older UV clarifiers before 2011 and does not fit any of the pressurized filters. Only fits models 19523 (5 Watt); 19520 (9 Watt); 19521 (18 Watt); and 19522 (36 Watt) Includes 2 barbed swivel adapters, 2 collar rings and 2 o-rings This UVC adapter kit fits .75", 1" and 1.25" ID tubing